1. Field of invention
This invention relates to a lock structure for connecting two parts or members, such as connectors, together, and more particularly to a lock structure having a mechanism for canceling a locked condition.
2. Related art
FIGS. 9 and 10 show one known structure in which male and female connector housings or the like are connected together, and this connected condition is locked, and this locked condition is canceled. In this lock structure, a lock arm 37 is pivotally supported resiliently on the female connector housing 33 through a leg portion 35 at a generally central portion of the lock arm 37. A retaining portion 39 is formed at one end of the lock arm 37 while a cancellation portion 45 is provided at the other end thereof. A load is applied to the cancellation portion 45 by the finger to lift the retaining portion 39 of the lock arm 37, thereby canceling the engagement between the retaining portion 39 and a retaining portion 43 of the male connector housing 41. Such a lock structure is proposed in Japanese Utility Model Unexamined Publication Nos. 61-60482 and 3-39272. A lock structure, shown in FIGS. 11 and 12, is proposed in Japanese Utility Model Unexamined Publication No. 2-54180. In this lock structure, lock arms 51 are pivotally supported resiliently on a male connector housing 47 at their respective leg portions 49, and cancellation arms 53 are also provided on the male connector housing 47. A retaining portion 55 is formed at distal ends of the lock arms 51. The cancellation arms 53 are connected to the distal end of the lock arms 51, and extend beyond the leg portions 49 in a direction away from the retaining portion 55, and a cancellation portion 57 is formed at rear ends of the cancellation arms 53. Stopper portions 59 for preventing excessive depressing of the cancellation arms 53 are formed on the male connector housing 47. A load is applied to the cancellation portion 57 by the finger to lift the retaining portion 55 of the lock arms 51, thereby canceling the engagement between the retaining portion 55 and a retaining portion 63 of a female connector housing 61.
However, in the lock structure proposed in Japanese Utility Model Unexamined Publication Nos. 61-60482 and 3-39272, it is necessary to thicken the leg portion in order to increase the locking strength. However, if the leg portion is thickened, a large force is required for canceling the locked condition. In contrast, if it is desired to reduce the force required for canceling the locked condition, the leg portion must be thinned, and therefore the sufficient locking strength can hardly be obtained. Namely, the problem is that the increase of the locking strength is contradictory to the reduction of the force required for canceling the locked condition.
In Japanese Utility Model Unexamined Publication No. 2-54180, the cancellation arms are supported on the distal end portion (the retaining portion) of the lock arms, and therefore even when a force is applied to the cancellation arms, the retaining portion of the lock arms, in some cases, are not displaced in the canceling direction before the cancellation arms are brought into abutting engagement with the stopper portions, and therefore the canceling ability is low. Namely, the displacement of the distal end portion (the retaining portion) is not constant, but varies depending on the direction and angle of the force applied to the cancellation arms for lock-canceling purposes, and therefore the retaining portion is not displaced in the canceling direction, which results in a possibility that the locked condition can not be positively canceled.